import sys, time

from PyQt5.QtCore import QTime, Qt, QTimer
from PyQt5.QtWidgets import QApplication, QLabel

app = QApplication(sys.argv)
try:
    due = QTime.currentTime()
    message = "Alert"
    if len(sys.argv) < 2:
        raise ValueError
    hours, mins = sys.argv[1].split(":")
    due = QTime(int(hours), int(mins))
    if not due.isValid():
        raise ValueError
    if len(sys.argv) > 2:
        message = "".join(sys.argv[2])
except ValueError:
    message = "Usage:alert.py HH:MM[optional message]"  # 24hr clock

while QTime.currentTime() < due:
    time.sleep(20)
label = QLabel("<font color=red size=72 <b>" + message + "</b></font>")
label.setWindowFlags(Qt.SplashScreen)
label.show()
QTimer.singleShot(60000, app.quit)
app.exec()
